1. Field of the Invention
The present invention relates to digital broadcasting system and more particularly to digital broadcasting system including digital broadcasting receiver having recording and reproducing function of digital broadcasting program. In addition, the invention relates to digital broadcasting station and digital broadcasting receiver used for digital broadcasting system.
2. Background Art
In recent years digitization of television broadcasting is promoted in Japan and the beginning of BS digital broadcasting with the use of satellite is scheduled on and after the end of 2000 in Christian era. The digital broadcasting with the use of ground wave is also scheduled to begin on and after the end of 2003 in Christian era. In digital broadcasting, users are offered programs as digital information so that various services are available to users.
For example, in digital broadcasting, information associated with the program is set to be broadcasted whenever necessary from the digital broadcasting station. This program associated information includes program arrangement information. As for the program arrangement information, it is defined in standards “program arrangement information to employ in digital broadcasting” (ARIB STD-B10 Ver. 1.2) published by Corp. ARIB (Association of Radio Industries and Businesses). Program arrangement information includes fundamental information related to the program such as information of the program contents, information needed to make program table and frequency information assigned to the organized channel for broadcasting a program. Consequently, for example, a user can display program table at any time on the screen and select a desired program on the screen for watching.
In addition, the ARIB standard prescribes extended information of program arrangement information (named hereinafter as “program extended information”). This program extended information is an aggregation of plurality of tables such as LIT (Local event Information Table) and prescribes information with regard to local event. LIT is a table describing start time and finish time, etc of a local event. Local event corresponds to each part of a program which in the case is divided by time division like sport news in a news program. LIT is corresponded to one program by event identification expressed by 16 bits (event_id).
Consequently, digital broadcasting receiver of the user side can record only a part of one program (e.g. sport news in a news program) by referring to the program extended information. To be concrete, when a certain local event is indicated recording by a user, digital broadcasting receiver specifies the program based on event identification in the program extended information to extract and record local event in the program.
In addition, there may be a case that the program extended information includes ERT (Event Relation Table). ERT prescribes a relationship among plurality of programs and/or plurality of local events and it is corresponded to event relation identification (event_relation_id) expressed by 16 bits. For example, paying attention to the top news of a news program broadcasted at a fixed time every day, we can find a relevance between local events related to the top news. So, the program extended information prepares ERT to prescribe this relevance.
Consequently, digital broadcasting receiver can record only the top news of a news program which, for example, is broadcasted at a fixed time every day by referring to program extended information. To be concrete, event relation identification described by ERT concerned is also described by LIT. Reading the event relation identification described by LIT, digital broadcasting receiver accesses ERT to identify other local event related to the local event corresponding to LIT concerned. In this case, digital broadcasting receiver specifies LIT based on the event identification to acquire information with regard to the local event. Digital broadcasting receiver records the each local event afterwards based on user's recording indication of serial local events
As described above, in the digital broadcasting system, only the event identification is the index to specify a program in case of using the program extended information. However, as the event identification is expressed by 16 bits, conventional digital broadcasting system can merely identify about 65000 programs. Therefore, supposing that the program is changed every 30 minutes for example, a calculation shows that all of a bit pattern for event identification comes to be used up in less than 4 years. In addition, since some program finishes within one minute or five minutes, if event identification is assigned to such programs, all of a bit pattern for event identification may come to be used up in less than a year.
Accordingly, so far as practical use is concerned, same event identification once assigned to a program is recycled to another program after 24 hours passed since closing of the broadcasting program. For example, this practical use is described in BS digital broadcasting operative normal published by ARIB (TR B15 Ver.10).
However, according to the practical use, one event identification shows two or more programs after 24 hours passed since closing of a certain broadcasting program. Therefore, if program extended information is not broadcasted before or after less than 24 hours of a certain broadcasting program, the program can not be specified uniquely in digital broadcasting receiver. In other words, even if program associated information of the program is provided to digital broadcasting receiver after 24 hours passed since closing of a certain broadcasting program from the digital broadcasting station, the program cannot be specified uniquely in the digital broadcasting receiver. Therefore, there remains a problem that transmission flexibility of the program extended information is held in low level.
For example, when having broadcasted a program prescribing the expiry date such as including prize corner or a program including the contents to be corrected, broadcaster sometimes manages to update the program extended information of the program. The reason is because such program as above may probably be recorded in digital broadcasting receiver and so in this case meaningless information is provided to users when they reproduce the recorded program. However, if the program extended information is updated after more than 24 hours passed since broadcasting, program which differs from the event identification included in the program extended information comes to be identified. Therefore, the broadcaster must update program extended information after closing of the broadcasting program within less than 24 hours and so a great time constraint is added.
Incidentally, in order to deal with this, it is conceivable for example the expansion of the number of bits used for the event identification. According to this architecture, because the number of programs capable of being identified by event identification can be boosted, even if event identification is not recycled after 24 hours passed since the closing of broadcasting program, the program comes to be identifiable. Consequently, the digital broadcasting station can transmit the program associated information at any timing.
However, as the event identification is employed not only by the table composing program extended information but also by a great number of tables composing program arrangement information, it is necessary to extensively modify software or the like of the digital broadcasting receiver already designed or shipped. Therefore, it is virtually impossible to expand the number of bits used for event identification.